Typically, a user cloud host has several virtual disks. A virtual disk is a software component that emulates an actual disk storage device. The virtual disks can be formed by a local physical machine, or the virtual disks can be formed by cloud storage devices. Also, the virtual disks can be formed by a disk snapshot. In practice, the sizes of virtual disks in a system are often equal (for example, the sizes of the virtual disks when they are created are typically of fixed types and thus are typically the same). When the virtual disks of equal size are simultaneously mounted onto a user cloud host, it can be difficult to identify which specific virtual disks in a physical machine system correspond to the logical partitions in a user virtual machine (VM). In other words, the user has trouble determining mapping relationships of logical partitions to the virtual disks. This confusion affects the backup operations of key data disks and can lead to data back-up omissions, which in turn can put data disaster recovery at risk.